Fragrance-containing plastic coating compositions for paper substrates

ABSTRACT

A fragrance-containing coating composition for paper substrates consists essentially of a polyvinyl chloride (PVC) plastisol and one or more fragrances, for example, an insect repellant. The PVC plastisol contains an adhesion promoter when the paper substrate is a calendered and/or coated paper substrate. The coating is fused at about 320° F. for 15-30 seconds. The coated paper is stored in barrier bags.

RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 09/026,256, filed Feb. 19, 1998 now U.S. Pat. No.6,270,753 and entitled FRAGRANCE-CONTAINING PLASTIC COATING COMPOSITIONSFOR PAPER SUBSTRATES.

BACKGROUND OF THE INVENTION

Paper has been used as a substrate for fragrances. Many examples ofpaper-based fresheners may be found on the market. However, thecombination of fragrance(s), paper, and adhesives has not been feasiblebecause fragrances are good solvents. When a fragrance is absorbed intothe paper substrate, any adhesive bond with the paper substrate isdestroyed. Either the adhesive is dissolved or it is softened to thepoint where the adhesion is lost.

Also, fragrance—impregnated paper exhibits problems of maintainingfragrance quality and controlled release. Therefore, there is a need fora fragrance-containing composition which can be coated on the surface ofthe paper to exhibit both controlled release of the fragrance andcontrolled absorption of the fragrance into the paper, and which willnot penetrate to the back of the paper.

SUMMARY OF THE INVENTION

A fragrance-containing coating composition for paper substrates consistsessentially of (a) a polyvinyl chloride plastisol and (b) one or morefragrances. The PVC plastisol is a dispersion which typically containspolymer and a plasticizer(s). The paper substrate can be anon-calendered, non-coated porous paper, a coated, non-calendered paper,or a calendered, optionally coated paper. When the paper is calenderedand/or coated the polyvinyl chloride plastisol further contains anadhesion promoter.

The fragrance can be a fruit fragrance, a citrus fragrance, a floralfragrance, a woody fragrance, a leather fragrance, an orientalfragrance, a mint fragrance, and/or a food fragrance. A preferredfragrance is a mixture of insect repellents present in an amountsufficient to repel insects such as flies, mosquitos, and the like.

The coating composition may further consist essentially of a diluent aswell as a component which has a synergistic effect when combined withthe fragrance(s), e.g., dibutyl phthalate, a pigment, and/or a glitter.

The coating composition is applied at room temperature to at least oneside of the paper substrate as a film. The coated paper substrate israpidly heated at a temperature (e.g., 320° F.) and for a time (e.g.,15-20 seconds) sufficient to fuse the film to a clear coating and adhereit to the paper substrate without volatilizing the fragrance(s). Theheated paper substrate is then cooled and stored until use in a barriermaterial such as polyethylene terephthate-coated polyethylene, or analuminum-coated polyethylene. One side of the paper substrate may becoated with a pressure sensitive adhesive prior to coating when thepreferred PVC plastisol is used.

The advantages of the above coating composition include good adhesion tothe paper substrate, rapid drying under conditions which do notadversely affect the fragrance(s), clarity on drying which is importantwhen graphics are present on the paper, and, compatibility with allpaper grades. In addition, the plastisol has a low odor, has a low or nosolvent content, is compatible with a wide range of fragrances, and willaccept reasonably high levels of fragrance(s) and still retain thefragrance's notes.

This new plastic coating maintains fragrance quality, coating clarity,and paper adhesion and is useful for coating all grades of paper.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, the term “porous papers” refers to papers such as replycards which are not calendered or coated.

As used herein, the term “papers with a vellum finish” refers to paperswhich are not calendered for smoothness. These papers have fibersprotruding from the surface and are not coated.

As used herein, the term “coated paper substrates” refers to paperswhich are calendered for smoothness as well as papers which arecalendered and clay-coated. Such papers may be matte finish, dullfinish, regular finish, and cast-coated finish types. Papers with amatte finish are coated with an aqueous clay formulation consistingprimarily of clay and optionally titanium dioxide. Papers with a dullfinish are clay coated and calendered to provide a slight sheen on thesurface. Papers with a regular finish have a heavy clay coating which isbuffed and calendered for gloss. Papers with a cast-coated finish havethe regular finish discussed above and are provided with additionalcalendering and/or coating to provide a mirror-like finish.

As used herein, the word “fragrance” refers to a mixture which provide aliquid with a pleasing odor. The fragrance may include two or morecomponents and optionally a fixative or synergistic component whichincreases the fragrance's odor and permits the use of smaller amounts ofthe fragrance component(s).

As used herein the word “plastisol” refers to thermoplastics whichrequire heat for fusion. Plastisols are dispersions which have a “milky”appearance. Prior to fusion, the plastisol film coated onto thesubstrate is “cloudy” or “milky”. After fusion the plastisol film iscompletely clear. A “cloudy” or “milky” appearance indicates incompletefusion.

Polyvinyl chloride (PVC) plastisols suitable for use herein containpolymers, plasticizers, and, when the paper is a smooth and/or coated,non-porous paper, an adhesion promoter or enhancer. The preferredpolyvinyl chloride plastisol for smooth non-porous papers is a white orcolored liquid which is available from Rutland Plastics Technologies,Inc. (Pineville, N.C.) under the trade name NG0026 Thermo-O-Line. It hasa gel point of 165° F. and a flash point of >400° F. It should be storedat 65-97° F. to avoid “gelling”. Pigment concentrates may be added tothis plastisol in amounts of up to about 10-15% by weight if a tintedplastisol is desired.

Typically the coating thicknesses range from about 2-50 mils, preferablyabout 2-20 mils.

The maximum amount of fragrance which can be used is that amount whichis soluble in the PVC plastisol and which does not destroy thefilm-forming properties. The minimum amount of fragrance is that amountwhich is required to provide a fragrance strong enough to last for thedesired period of time. The amount of fragrance added to the PVCplastisol coating composition is 1.0 to about 20%, preferably about 6%to about 15%, most preferably about 13%, by weight, which amount willdepend upon the particular fragrance(s) selected.

Fragrances in all odor categories are useful herein, for example, fruitfragrances such as strawberry, raspberry, peach, cherry, apple and pear;citrus fragrances such as orange, lemon, grapefruit, and lime; floralfragrances such as rose, hyacinth, lilac, lily-of-the-valley, calyx,osmanthus, orange blossom, apple blossom, rose, and freesia; woodyfragrances such as cedarwood, sandalwood, oak, and pines; leatherfragrances, i.e., dominant notes from the quinoline family; orientalfragrances such as musk, vanillin, laubdanum, and oak moss notes;aldehydic notes; mint fragrances such as spearmint and peppermint; andfood fragrances such as vanilla, chocolate, chocolate mint, pizza,popcorn, barbecued meats (beef and chicken).

In many cases there is more than one way of achieving a particularfragrance type. A typical fragrance composition is composed of top-,middle-, and bottom-notes. The top-note(s) are the most volatile. Thebottom-notes are the least volatile and are the residual on the surfacewhich gives the fragrance a lasting quality. However, all of the notescontribute to the perception of the fragrance. For the type of usedescribed herein, heat-stable fragrances are preferred.

A preferred fragrance area is insect repellant which have beenformulated to contain a mixture of volatile natural and/or syntheticcomponents which are referred to as fragrances because of theirvolatility and olfactory properties. As with the above fragrances, therepellant can be constructed of top-, middle-, and bottom-notes.

To be acceptable, the insect repellant must be long lasting and thisquality is influenced by the PVC plastisol carrier. Preferably, thefragrance is formulated to contain more than one insect repellant.Insects which can be repelled include house flies, mosquitoes, yellowjackets, and ants.

Natural ingredients which act as insect repellants include salicylates,benzoates, lemon and orange oils, citronella oil, geraniol, terpineol,garlic oil, grapefruit oil, mints, southernwood, and tea tree oil.

The above insect repellents are used in amounts ranging from 0.3 togreater than 20% in a finished formula depending upon the repellencyproperties sought and the odor properties desired. For example, in therange of 0.3 to 1.0% one may use geraniol, lavender oil, camphor oil,and/or cinnamon oil; in the range of 1.0 to 10.0% one may use variousacetates, citronella oil, lemon oil, orange oils, and terpineols; and inthe range above 10% one may use lemon or orange oils and benzoates.Inert diluents such as glycols, alcohols, and/or phthalates, may be usedfor cost control.

Because the coating after fusion is glossy and transparent, it isparticularly useful on printed paper substrates because the graphics canstill be easily seen.

Preferably, a single coating having a thickness of about 2-50 mils.,preferably about 2-20 mils., is applied at room temperature to onesurface of the paper substrate. The thickness of the coating should notbe thicker than that which can be fused during heating. If desired, morethan one coating can be applied provided the coating is allowed to drythoroughly between coatings. If desired, both sides of the papersubstrate can be coated, in which case less fragrance will be needed toobtain the desired effect.

The coating is set by quickly heating the coated paper substrate. Forexample, the coated paper substrate is placed on a movable belt andquickly moved through a heating tunnel where the peak temperature issufficient to fuse the film. Typically the peak temperature is about320° F.; the exposure time to this temperature depends upon thethickness of the film. If the film is about 2 to about 4 mils inthickness, the fusion time will be about 15 seconds. The peaktemperature and residence time in the tunnel should be sufficient toprovide a clear, not “milky” , coating.

After cooling the fused coated paper substrate can be cut into anydesired shape. If desired, a tacky adhesive can be applied to theuncoated side of the paper substrate before or after the coating so thatthe coated product can be adhered to a person's clothing or otherobject. If not used immediately, the fragrance-coated substrate shouldbe packaged so the fragrance does not prematurely evaporate from thecoating. Evaporation is prevented by covering the coated paper substratewith a barrier material such as polyethylene terephthalate-coatedpolyethylene or aluminum-coated polyethylene, and the like.

EXAMPLE 1

This example describes the preparation of a fragrance which is a naturalinsect repellent and its inclusion in the polyvinyl chloride (PVC)plastisol which is sold under the trade name NG0026 Thermo-O-Line byRutland Plastic Technologies.

The fragrance was obtained by mixing the following ingredients:

Ingredient Wt. % Eucalyptus Oil 0.3 Cedarwood Oil 0.7 Citronella Oil10.0 Pine Oil 25.0 Camphor Oil 1.0 Linalool 1.0 Linalyl Acetate 1.0Lemon Oils 10.0 Phenylethyl Alcohol 7.0 Terpineol 3.0 Galbanum Oil 1.0Benzyl Acetate 15.0 Turpentine 2.0 Patchouli 5.0 Benzyl Alcohol 2.0Isoamyl Salicylate 1.0 Isopropyl Myristate 2.0 Isopropyl Palmitate 4.0Dipropylene Glycol 9.0 100.0%

A total of 10% (w/w) of the above fragrance was included in the PVCplastisol. One gallon was sufficient to coat 325 square feet of thepaper.

The coating thickness was 4 mils. For testing 1 square inch portions ofthe paper were coated and the coating was fused at 320° F. for 15seconds, cooled, and placed in a barrier bag. The coating parameterswere chosen to provide a product life of 8 hours. The aroma wasevaluated after storage in the barrier for 5 days. After storage in thebarrier bags for 5 days, the coated paper samples were taken out andplaced on a flat surface. The odor of the samples was evaluated over aperiod of 24 hours at which time the test was discontinued.

All of the papers listed below are calendered papers. Some are coatedand some are embossed and uncoated. All are 65-80 lbs. stock.

The results are summarized below.

Substrate Organoleptic Evaluation Textured Paper Ultrafelt Text Goodinitial fragrance strength and (acid-, alum-, and rosin-free) goodfragrance retention Pageantry Cover Canvas Good initial fragrancestrength and (uncoated) good fragrance retention Champion Cordwain CoverGood initial fragrance strength and (uncoated) good fragrance retentionChampion Linen Cover Good initial ,fragrance strength and good fragranceretention Champion Felt Cover (alkaline sheets) Irish Linen CoverFragrance perceived was missing top (acid-, alum-, and rosin-free) notesinitially and fragrance faded rapidly George A. Whiting Fragranceperceived was missing top (acid-free, 100 % recycled) notes initiallyand fragrance faded rapidly Smooth Paper Augusta Bristol Good initialstrength and good retention (0.007) Augusta Bristol Good initialstrength and good retention (0.008) Augusta Bristol Good initialstrength and good retention (0.009) Hammermill Cover WeyerhauserFragrance perceived was missing top Husby Smooth Scott notes initiallyand fragrance faded with time Appleton Crystin Cover (coated Fragranceperceived was missing top paper) notes initially and fragrance fadedrapidly Pageantry Cover Vellum Fragrance perceived was missing top(uncoated) notes initially and fragrance faded rapidly

EXAMPLE 2

The fragrance described in Example 1 is added at 10% (w/w) to an opaque,high viscosity, white polyvinyl chloride (PVC) plastisol which is soldunder the trade name NH-LB LOW-BLEED by Rutland Plastic Technologieswhich has a gel point of 165° F. and a fusion temperature 320° F. Thefragrance containing PVC plastisol is coated onto vellum, reply cards,or other uncalendered papers using an amount sufficient to provide acoating having a coating thickness of about 2-20 mils. The coating isfused at 320° F. for about 15 seconds, cooled, and stored in barrierbags.

Now that the preferred embodiments of the invention have been describedin detail, various modifications and improvements thereon will becomereadily apparent to those skilled in the art. Accordingly, the spiritand scope of the present invention are to be limited only by theappended claims and not by the following specification.

What is claimed is:
 1. A method of coating a paper substrate, whichcomprises the steps of: (a) applying at room temperature to at least oneside of the paper substrate a film of a coating composition consistingessentially of (a) a polyvinyl chloride plastisol and (b) one or morefragrances; (b) rapidly heating the coated paper substrate at atemperature and for a time sufficient to fuse the film to a clearcoating and adhere it to the paper substrate without volatilizing thefragrance(s); and (c) cooling the heated paper substrate; wherein thecoating is applied in an amount sufficient to provide a continuouscoating which will adhere to the paper and release the fragrance overtime.
 2. The method of claim 1, wherein the polyvinyl chloride is adispersion containing polyvinyl chloride polymers, one or moreplasticizers, and an adhesion promoter.
 3. The method of claim 1,wherein the paper substrate is a porous paper substrate or anon-calendered paper.
 4. The method of claim 1, wherein the papersubstrate is a calendered and/or a coated paper substrate and whereinthe coating further consists essentially of an adhesion promoter.
 5. Themethod of claim 3, further comprising the step of packaging the coatedpaper substrate in a barrier material selected from the group consistingof polyethylene terephthate-coated polyethylene and an aluminum coatedpolyethylene.
 6. The method of claim 1, further comprising the steps ofcoating the uncoated side of the paper substrates with a pressuresensitive adhesive.
 7. The method of claim 1, wherein the heating iscarried out at about 320° F. for a period of time sufficient to yield aclear coating.
 8. A paper substrate coated with a fused polyvinylchloride film containing an effective amount of one or more fragrances.9. The paper substrate of claim 8, wherein the substrate which is coatedis a non-calendered paper substrate and the fragrance is an insectrepellent.
 10. The paper substrate of claim 8, wherein the substratewhich is coated is a calendered and/or coated paper substrate and thefragrance is an insect repellent.